1. Field of the Invention
This invention relates to improvements in electroluminescent lamps, particularly to an improved electrical contact configuration for use with flexible electroluminescent lamps.
2. Description of the Prior Art
One type of electroluminescent lamp comprises a laminate of a layer of particles of electroluminescent phosphors in an organic resinous binder sandwiched between electrode layers, one electrode layer of which is transparent to the light emitted by the phosphor. In the prior art, the transparent light emitting electrode is generally either a layer of transparent metal oxide such as tin oxide or indium oxide, or a deposit of a thin metal layer. In any event, a compromise must generally be made between the light transmissivity and the conductivity of the electrode. Until recently, this compromixe has precluded the formation of a thin-film electrode having acceptable levels of transmissivity and conductivity. However, the development of a multiple layer transparent electrode such as that disclosed in my co-pending patent application, Ser. No. 673,680, filed Apr. 5, 1976 overcomes such limitations. While a suitable transparent electrode is there disclosed, a reliable electrical connection thereto enabling the uniform distribution of an electrical potential across the electrode has remained a problem. In U.S. Pat. No. 3,231,664 (Acton) there is depicted an electrical contact to similar thin-film conductive layers which includes a relatively thick insulating separating layer. Such a layer is intended to apparently prevent the bond between the thin-film layer and another conductive layer from adversely affecting the properties of the first thin layer, but does not assist in providing a uniform distribution of electrical potentials. In U.S. Pat. No. 3,497,750 (Knochel and Wollentin) there is depicted a flexible electroluminescent lamp in which contacts to the transparent electrode are provided via a copper mesh electrode which is anchored directly to the transparent electrode by conductive cements or pressure contacts. Again, such structures do not solve the problem of providing reliable contact which uniformly distributes potential over the surface of the transparent electrode.